ASME规范中tube和pipe定义的解释(部分)
哈尔滨锅炉厂有限责任公司 梁剑平

        自ASME规范引进以来,它的第Ⅰ、Ⅱ、Ⅷ篇已成为锅炉行业必不可少的参考标准。在一段时期应用与消化之后,对这个标准的理解也逐渐深入,对其中某些翻译名词的困难,也逐渐溶化,比如tube和pipe的认识也逐渐加深。
Tube pipe在中文里都是“管子”或“管道”的意思,无法区分,而ASME规范却有不同的要求。在ASME规范第Ⅰ篇中有两个最基本的公式:
        对tubing按公式PG-27.2.1计算壁厚
       
        对tubing按公式PG-27.2.2计算壁厚
       
        计算要求和结果都不一样,这就必然涉及到中文tube和pipe的理解和区别问题。同是管子,什么是tube?什么是pipe?长期以来,技术人员根据各自的经验和对ASME上下温的理解与推测,也有不同的区别方法。
        第一种按管径尺寸来区分,5英寸或6英寸以下为tube,这样方法大部分人认可。
        第二种按管截面形状来区分,圆形截面归pipe,其它形状归tube。这种说法是由ANSI B31.1一段话推论来的,但很不严格。
        还有其它区分方法,如从工艺观点、平均壁厚公差等观点来区分。这些方法大多为推测性质,没有正宗来源。
        在美国,有幸就教于美国国家检验法规委员会委员、ASME委员会委员史汀老先生(E.A.Steen)的过程中,曾就这个问题提出疑问。史汀老先生认为,如何区分tube和pipe的问题,在不少其它国家都发生过,德文、西班牙文等都只能将tube和pipe翻译成同一单词“管子”或“管道”,很难区分。在应用PG-27.2.1和PG-27.2.2公式上界限很模糊,其实ASME在制定这段规则时并不着眼与管径大小或管子截面,而是着眼于管子或管道用途的性质。在锅炉和压力容器范围内,tube主要着眼于内外传导热量、热交换用途,而pipe则主要立足于将受压介质从一个地方输送到另一个地方的功能,这样pipe性质的管子上一般还都连着各种附件(三通、弯头)和阀门。
        从这观点来看,省煤气管、水冷壁管等必属于tube类,而主蒸汽管道、下降管等或其它连有三通、阀门管路的则必属pipe类。为了进一步澄清这个认识,史汀老先生还热情地找出两份ASME委员会就有关这个问题的正式文件。如下:

文件一:
Interpretation:1-83-47
Subject:Section 1,PG-27, definition of Pipe and Tube
Date issued:August 8,1979
File:BC79-501
Question: Do the rules of PG-27.2.2 define tubing and piping, respectively, by size only, or are there other criteria?
Reply: The formulas in Section 1, PG-27.2.1 ,for tubing are intended primarily for applications such as boiler tubes, or economizer tubes in which groups of such tubular elements are arranged within some enclosure for the purpose of transferring heat to or from the fluid within the tubes. For this heat transfer function, the tubular elements ordinarily do not need fittings or valves.
When the function to be performed is mainly the conveying of a pressurized fluid from one location to another, with litter or no intentional heat transfer, the tubular elements commonly used for this purpose are called piping. The standard piping sizes are available with the matching sizes of fittings (tees , elbows, etc.) and valves to facilitate the installation of piping systems to direct and control the flow. For such application, the formula for piping wall thickness in Section 1, PG-27.2.2 (or ANSI B31.1, Paragraph 104.1.2) , should be used.

文件二:
Interpretation:1-86-25
Subject:Section 1, PG-27.2, wall Thickness of Pipe and Tube
Date:June 23, 1986
File:BC81-713, BC83-289, BC83-669, BC84-230
Question: Under what circumstances do the equations under PG-27.2.1 (for tubing) and PG-27.2.2 (for piping) apply?
Reply: The formulas in ASME Section 1, PG-27.2.1, for tubing, are intended primarily for applications such as boiler tubes, superheater and reheater tubes, or economizer tubes in which groups of such tubular elements are purpose of transferring heat to or from the fluid within the tubes. For this heat transfer function, the tubular elements ordinarily do not need fittings or valves.
When the function to be performed is mainly the conveying of a pressurized fluid from one location to another, with litter or no intentional heat transfer, the formulas in PG-27.2.2 should be used. The elements commonly used for this purpose are called piping. The standard piping sizes are available with matching sizes of fittings (tees, elbows, etc.) and valves to facilitate the installation of piping systems to direct and control the flow.

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